Steam boiler and pressure control



Aug. 4, 1942. J. E. BRANT LY 2,291,872 STEAM BOILER AND PRESSURECONTROL- Filed Feb 5, 1940 Patented Aug. 4, 1942 1 ilNlTED ENT OFFICE 11Claims.

This invention has to do with improvements in steam boilers, and has forits primary object to provide for such increased heating efficiency,economy and responsiveness to varying load requirements as to adapt theboiler to uses and methods of operation for which theusual boilers areunsuited by reason of their lower heating fiiciencies and inability topromptly develop steam pressures in accordance with varying loads. Thepresent application is a continuation-in-part of my copendingapplication Ser. No. 210,896, on Steam boiler, allowed July 14, 1939,now Patent No. 2,189,443.

Ordinarily in the operation of boilers supplying steam for varying loadsand at ccrrespond ingly varying pressures, the boiler steam pressure isheld at some constant value sufficient to handle the maximum load.Muchof the time however the boiler may be operating under considerablyless load with resultant wasted energy by reason of the nonworkingreduction of steam pressure from the maximum or constant pressuremaintained in the boiler, down to the lower pressure required to operatethe work. A familiar example where the load may vary from comparativelylittle, requiring low steam pres-- sure, up to heavy loads-requiringhigh steam pressure (the constant pressure maintained in the boiler) isin well drilling operations where the mud pumps and other equipment aresteam operated and th load varies widely in accordance with the depth ofdrilling and the particular operations at any one time. In view of theloss of heat and pressure energybecause of having to maintain, much ofthe time, a considerably higher boiler pressure than is requiredto-operate the work, it is apparent that the efficiency of any plantoperating in this manner might be greatly improved were it possible tomaintain the boiler pressure in correspondence with the necessaryworking pressure, and to vary the boiler pressure as such necessaryworking pressure changes.

Insofar as I am aware it hasnot been possible heretofore, at least inthe use of heavy duty boilers, to operate by the method and under theconditions last stated, due to the inability of the ordinary boilers togenerate-steam at suflicient rate to meet varying load requirements.Accordingly the present invention has been made with that object inview. The invention is particularly applicable to forced draft boilers,and specifically where primary air is supplied to the burner undervariable pressure, by reason of the desirability for intense firing andheat generation and rapid changes in the rate of heat generation inaccordance with load requirements. In the broad aspects of the inventionthe boiler may be of any suitable type or design provided with means formaintaining positive internal flow or circulation of water along wallsor surfaces through which heat is transmitted from the burner combustiongases.

Broadly the boiler may be described structurally as comprising a burnerfired heating chamber or space, walls through which heat is transferredfrom the heating chamber to water in the boiler, and means formechanically producing a flow of water along said walls. Preferably Iemploy a power dri-Venpump operating to maintain a rapid flow of wateralong heating surfaces in the boiler, and control the speed of the pump,and therefore the rate of water flow along the heating surfaces (andconsequently the rate of steam generation), in accordance with theboiler steam pressure. The ratesof fuel and air supply to the burner aresimilarly controlled so that both the-rates of water circulationand airand fuel supply vary as the boiler steam pressure changes, andconversely, both mayb varied to control the boiler steam pressure. By.virtue of forceddraft firing and the maintenance of rapid watercirculation along the heating, surfaces in the boiler, provision is madefor highly efiicient and rapid steam generation, and by rendering thesefactors controllable, andrvariable by the operator .it becomes possibleto regulate and vary the boiler steam pressure inv accordance with theload, rather than having to maintain a fixed boiler pressure that maygreatly exceed the necessary working pressure, as is customarily thecase.

Water circulationv may be maintained 'within the boiler by a pressurecontrolled pump of the type disclosed in my Patent No. 2,189,443 andwhile, as previously stated, any suitable type and form of boilerconstruction may be used, I prefer in order to obtain maximum heateconomies and heat transfer rates, to employ a boiler of a type in whichthe fire box is jacketed by a water. and

steam containing space, as for exampleshown in the application referredto, and also inmy recent application Ser. No. 315,031, filed January 22,1940, on Steam boiler.

A more complete explanation and understanding of the invention will behad from the detailed description to follow and throughout reference ishad to the accompanying drawing illustrative of the invention in one ofits typical and preferred forms. a

The drawing shows a Vertical type boiler comprising an inner fire box I9containing a combustion chamber or heating space I I, surrounded by andenclosed within an outer shell I2 which is annularly spaced from thefire box to form an upper steam chamber I3 and a water leg I4 withinwhich water is circulated, as will later appear, along the outer surfaceof the fire box wall. The fire box I comprises a cylindric shell Illahaving a segmental hemispherical head Iflb through which the combustiongases flow to the stack [5. The outer shell I2 similarly comprises acylindric section I2a and a segmental hemispherical head I 2b welded toa tube section I6 exposed to the steam chamber I3 and spaced from thestack I5. The boiler may be thermally insulated by a jacket I! ofsuitabl heat insulating material, the insulation being placed also in aspace IIa between wall I8 and the stack I and also at I8 about the stackbelow the air preheater I9.

The boiler structure is supported on a suitable base comprising anintermediate floor 2| having a central opening 22 to receive theconventionally illustrated burner 23. understood, the burner may be ofany suitable type, including one or an assembly of individual burnerunits such as are customarily used, capable of high capacity and intenseheat generation. It is desirable to employ a type of burner capable ofproducing combustion of the gas or other fuel in a short intense heatflame to avoid flame impingement against the water tubes. The floor 2|supports an annular shell 24 within which is placed a fire brick wall 25about theburner opening 22. Suitable provision may be made for supplyingprimary air to the burner, as through a conduit 26, the particular formand arrangement of which may vary in accordance with the particular typeand design of the burner. Ordinarily it will be preferred to supply allthe burner air through conduit 26, and normally under pressure so thatthe boiler operates under forced draft. If for any reason desired,secondary air may be supplied by leaving a space at 21 between theburner and the surrounding wall.

Supported on the top of the base 20 is an annular water chamber 28formed by an annular tube 29 of curved, and for the most part circularcross section, Welded at 30 to the bottom of shell I2a and having ahorizontally extending top portion 3I welded to the shell at 32. Theboiler feed water introduced through line 33 may be preheated bycirculation through coil 34 in the stack I5 and then discharged throughline 35 under control of the conventionally illustrated liquid levelregulator 36 to chamber 28. Normally closed hand holes 31 are providedat suitable intervals in the bottom of the water chamber shell 29 tofacilitate cleaning the chamber and to permit access to the lower endsof the water tubes.

The heating chamber II contains a series of circularly arranged watertubes 38 of segmental circular curvature, the upper and lower ends ofwhich extend at 39 and 40 through the fire box crown sheet I01) andshell 29 to permit circulation of water from the water chamber upwardlythrough the tubes into the steam chamber I3 and Water leg I4. A baiile42 positioned at the longitudinal centers of tubes 38 serves to directthe upwardly flowing combustion gases in the paths indicated by thearrows, outwardly along the fire box shell Illa, thus increasing therate of heat transfer through the fire box shell to the water flowingalong its outer surface in the water le As Will be I4. Leaving chamberII, the gases flow upwardly into the stack in contact with a superheater coil 43 having an inlet at 44 through which the steam flows fromchamber I-3 to be super heated in the coil and then discharged throughthe outlet line 45. Where superheating is not desired, the steam may betaken directly from chamber I3 through pipe 46 to line 45.

A portion of the feed and recirculated water is discharged directly fromchamber 28 upwardly through nozzles 41 into the lower portion of thewater leg I4 at the inside of an annular cylindric bafile 48. The waterdischarged from the nozzles 41 flows upwardly along the outer surface ofthe fire box shell I Ila in high velocity streams, by reason of thenozzle discharge velocity and the stream confinement between the firebox and baffle. The maintenance of water circulation in space 49 thusserves to efiectively remove steam bafiles and immobile films from theheating surface of the fire box and thereby to maintain maximum heattransfer rates from the heating chamber I I to the surrounding water.

Positive circulation of water from chamber 28 upwardly through tubes 38,and return water circulation from the water leg I4 to chamber 28, ismaintained by a suitable pump, conventionally illustrated at 50, havingan inlet lin 5I leading at 52 from space 53 at the outside of bafile 48,and an outlet line 54 discharging at 55 into the water chamber. Aby-pass line 56 and suitable valves 51, 58 and 59 may be provided sothat if desirable at any time, convection or thermo-syphonic circulationmay be maintained without using the pump. A will be apparent, the pumpoperates to maintain positive and high velocity circulation of waterfrom chamber 28 through the water tubes 38 and through nozzles 41 withinthe inner space 49 of the water leg. The pump draws water from thedownflowing circulation in space 53 at the outside of the bafile, thelatter thus preventing interference by the water flowing to the pum withthe upwardly flowing stream at the outside of the fire box.

Pump 58 may be driven by any suitable means, as by the conventionallyillustrated motor or turbine 60 which may be either electrical or steamoperated and so controlled that its speed, and therefore the speed ofthe pump 50, varies or is variable in accordance with the changes in theboiler steam pressure or desired variations in that pressure. Typically,the motor or turbine speed may be controlled by a suitable pressureoperated regulator 6 I, particular types of which are known and incommon use, to which the boiler steam pressure is communicated throughline 62 above the boiler water gauge 63. The regulator or governor BImay control the supply of electric current through lines 64 Where themover 69 consists of an electric motor, or it may control the supply ofsteam through lines which may be taken as illustrated by 64, Where themover 60 consists of a steam turbine or engine.

The supply of primary air to the burner 23 is similarly controlled inaccordance with variations in the boiler steam pressure, or desiredvariations in that pressure, by operating blower 65 in the air supplyconduit 26 in essentially the same manner as the water circulation pump50. For maximum heat efficiency in the operation of the boiler theburner air is passed from supply pipe 66 through preheater I9 whereinresidual heat from the combustion gases is transferred to thebur-nersupply air and the gasesare reduced to a low temperature. Typically thepreheater I9 is shown to comprise an outer annular jacket 6-! about thestack and horizontal tubes 68 extending through opposite sides of thestack. After becoming preheated in flowing through the jacket and tubes,the air flows through conduit 69'to the blower 65. The latter may bedriven by motor 60 and the air supply to the burner thus controlled inaccordance with the motor speed and boiler steam pressure, or the blowermay be driven by an independent mover controlled in its operationsimilar to motor 60.

Assuming the control 6| to be set to maintain a predetermined constantboiler steam pressure, as the rate of steam withdrawal from the boilerdrops the-pressure, the control 6| operates to increase the speed ofmotor 60, and therefore of the pump 50 and the blower 65, with theresult that the rate of water circulation in the boiler 2.

and the rate of heat supply from the burner are correspondinglyincreased. By reason of the immediate responsiveness of the control andthe prompt steam generating capacity of the boiler under such increasedwater circulation rate and intensified firing, the normal boiler steampressure is quickly restored. As that pressure is exceeded, the control6| operates to slow down or even stop the motor 60, thus reducing ordiscontinuing water circulation in the boiler and operation of theburner, except the usual pilot light, until the steam pressure drops tonormal.

The supply of fuel to the burner 23 similarly may be controlled inaccordance with the boiler steam pressures so that as the steam pressureexceeds a predetermined maximum, the burner fuel feed will be reduced ordiscontinued, and conversely as the steam pressure falls below thatpredetermined maximum. As illustrative, supply of gas to the burnerthrough line H is shown to be controlled by a conventionally illustratedvalve 12 operated by a pressure responsive control 18, which may be of adiaphragm or other suitable type, connected to the boiler steam chamberby line 13.

As previously explained, it becomes possible by reason of the relativelyquick responsiveness of the boiler to steam pressure requirements, tocontrol the operation of the boiler so that its steam pressure may varyto correspond with the necessary pressures required for varying loads.For this purpose, the control 6| may be manually regulated, as by lever10, so that as the pressure required to operate the work varies, theoperator may regulate the control 6| to cause, as

the case may be, increased or decreased rates of water circulation andheat supply by the burner. The control 6| may be of rheostat type whichpermits progressive changes in the motor speed, or it may be of a typeadapted to cause predetermined variations in the motor speedcorresponding, for example, to 10 to 25 pounds per sq. in. variations inthe boiler steam pressure. The supply of fuel to the burner may besimilarly controlled simultaneously and in accordance with variation bythe operator of the rate of water circulation and the rate of primaryair fiow to the burner, by any suitable means such as, for example, amanual control 12a for operating the valve 12. Thus the flow of gas tothe burner may be increased or decreased simultaneously with and inproportion to increased or decreased rate of primary air to the burnerall in a manner so as to maintain the proper fuel to air ratio for mostefficientcombustion and .intensity of heating.

I claim:

1. In a boiler, the combination comprising a fire box, an outer wallspaced from the fire box to form a steam chamber and a water legdirectly exposed to the side of the fire box wall, means forming a waterchamber communicable with said water leg, water tubes connecting-saidwater chamber with the space between said outer wall and the fire box, apump for circulating water from the water chamber through said tubes, aburner supplying hot gases to said fire box, a blower for dischargingair to the burner, and means for varying the pump and blower speeds inaccordance with variations in the boiler steam pressure.

2. In a boiler, the combination comprising a fire box, an outer wallspaced from the fire box, to form a steam chamber and a water legdirectly exposed to the side of the fire box wall, means forming a waterchamber communicable with said water leg, water tubes connecting saidwater chamber with the space between said outer wall and the fire box, apump for circulating water from the water chamber through said tubes andthrough an independent passage into said water leg, a burner supplyinghot gases to said fire box, a blower for discharging air to the burner,and means for varying the pump and blower speeds in accordance withvariations in the boiler steam pressure.

3. In a boiler, the combination comprising a wall forming a verticallyextending fire box, an outer wall spaced from said firebox to form asteam chamber thereabove and an annular water leg surrounding anddirectly exposed to the sides of the fire box wall, a water chamber atthe bottom of said water leg, water tubes extending from said waterchamber upwardly within the fire box through its top wall, a pumpoperating to discharge water from the water chamber through said tubes,a burner for supplying hot combustion gases to the fire box, a blowerfor discharging air to the burner, and means for varying the pump andblower speeds in accordance with variations in the boiler steampressure.

4. In a boiler, the combination comprising a wall forming a verticallyextending fire box, an outer wall spaced from said fire box to form asteam chamber thereabove and an annular water leg surrounding anddirectly exposed to the sides of the fire box wall, a water chamber atthe bottom of said water leg, water tubes extending from said waterchamber upwardly within the fire box through its top wall, a pumpoperating to discharge water from the water chamber through said tubes,a burner for supplying hot combustion gases to the fire box, means forpreheating air by combustion gases discharged from said fire box, ablower for discharging the preheated air to the burner, and means forvarying the pump and blower speeds in accordance with variations in theboiler steam pressure.

5. In a boiler, the combination comprising a fire box, an outer wallspaced from the fire box, an outer Wall spaced from the fire box to forma steam chamber and a Water leg directly exposed to the side of the firebox wall, means forming a water chamber communicable with said waterleg, water tubes connecting said water chamber with the space betweensaid outer wall and the fire box, a pump for circulating water from thewater chamber through said tubes, a

burner supplying hot gases to said fire box, a blower for dischargingair to the burner, and means for varying the pump and blower speeds inaccordance with variations in the boiler steam pressure, and means forsupplying fuel to the burner at a rate varying with changes in theboiler steam pressure.

6. In a boiler, the combination comprising a wall forming a verticallyextending fire box, an outer wall spaced from said fire box to form asteam chamber thereabove and an annular water leg surrounding anddirectly exposed to the sides of the fire box wall, a water chamber atthe bottom of said water leg, water tubes extending from said waterchamber upwardly within the fire box through its top wall, a pumpoperating to discharge water from the water chamber through said tubes,a burner for supplying hot combustion gases to the fire box, a blowerfor discharging air to the burner, means for varying the pump and blowerspeeds in accordance with variations in the boiler steam pressure, andmeans controlled by the boiler steam pressure for supplying fuel to theburner.

7. In a boiler having an outer shell and a heat is transferred from saidheating chamber to a water chamber inside said boiler shell andsubstantially surrounding the heating chamber, water tubes within saidheating chamber and communicating with said water chamber so that watercan circulate through said tubes and water chamber, means formechanically producing high velocity water circulation through saidtubes and water chamber and along said walls, and means for varying therate of said water circulation and the rate of fuel and air supply tothe burner in accordance with variations in the boiler steam pressure.

8. In a steam boiler having an outer shell and a steam outlet, thecombination comprising a burner for supplying hot gases to a heatingchamber within the boiler, means for preheating air by combustion gasesfrom said space and for supplying the preheated air to the burner, wallsthrough which heat is transferred from said heating chamber to a waterchamber inside said boiler shell and substantially surrounding theheating chamber, Water tubes within said heating chamber andcommunicating with said water chamber so that water can circulatethrough said tubes and water chamber, means for mechanically producinghigh velocity water circulation through said tubes and water chamber andalong said walls, and means for varying the rate of said watercirculation and the rate of air supply to the burner in accordance withvariations in the boiler steam pressure.

9. In a boiler having an outer shell containing a steam space, thecombination comprising a burner for supplying hot gases to a heatingchamber within the boiler, a blower for discharging air to the burner,walls through which heat is transferred from said heating chamber to awater chamber inside said boiler shell directly below said steam spaceand substantially surrounding the heating chamber, water tubes withinsaid heating chamber and communicating with said water chamber so thatwater can circulate through said tubes and water chamber, a

pump for producing high velocity water circulation through said tubesand water chamber and along said walls, and means for varying the speedsof said blower and pump in accordance with variations in the boilersteam pressure.

10. In a boiler having an outer shell and a steam outlet, thecombination comprising a burner for supplying hot gases to a heatingchamber within the boiler, walls through which heat is transferred fromsaid heating chamber to a water chamber inside said boiler shell andsubstantially surrounding the heating chamber, water tubes within saidheating chamber and communicating with said water chamber so that watercan circulate through said tubes and water chamber, means formechanically producing high velocity water circulation through saidtubes and water chamber and along said walls, means for varying the rateof said .water circulation in ac cordance with variations in the boilersteam pressure, and means for manually controlling and varying theboiler steam pressure.

11. In a boiler having an outer shell containing a steam space, thecombination comprising a burner for supplying hot gases to a heatingchamber within the boiler, means for supplying fuel and air to theburner, Walls through which heat is transferred from said heatingchamber to a water chamber inside said boiler shell directly below saidsteam space and substantially surrounding the heating chamber, watertubes within said heating chamber and communicating with said waterchamber so that water can circulate through said tubes and waterchamber, means for mechanically producing high velocity watercirculation through said tubes and water chamberand along said walls,means for varying the rate of said water circulation and the rates offuel and air supply to the burner in accordance with variations in theboiler steam pressure, and means for manually controlling and varyingthe boiler steam pressure.

JOHN E. BRANTLY.

